I've long believed that the X3 post credits scene was well crafted. Xavier is talking about a man born with no brain activity, no consciousness, so he asks about the ethics in regards to that and what he could do. Moira is a geneticist in the comics.

Personally, I think they were intentionally setting it up that they had cloned Xavier and it was basically a back up for him to transfer his consciousness to in case something happened. Cloned by Moira and Xavier kept the mind from developing so it was a blank slate.

Little out there and sci-fi-ish but fits pretty well for comic book standards.

Be nice if they explained that a little in DOFP though otherwise it's all just assumption